The present invention relates to a method of producing methanol synthesis gas.
More particularly, it relates to a method of producing methanol synthesis gas with a ratio of carbon monoxide to hydrogen defined by the desired synthesis reaction, by gasification (partial oxidation) of fine grained to dust-like fuels at temperatures above the slag melting point. The produced partial oxidation gas is indirectly cooled in a waste heat boiler located after the gasifier with production of steam, and then is subjected to dedusting, a catalytic CO-conversion, and a desulfurization.
Methods of producing of methanol synthesis gas of the above mentioned general type are known in the art. The partial oxidation crude gas produced during the gasification of fine-grained to dust-like fuels contains, depending on the composition of the used fuels and on the reaction conditions of the gasification, a ratio of carbon monoxide to hydrogen which can lie within the range between 1:1 to 2.7:1. However, for the methanol synthesis a methanol synthesis gas is required whose ratio of carbon monoxide to hydrogen must lie within the region of 0.4:1 to 0.5:1. For arriving at these values it is necessary to remove from the gas excessive CO by the CO-conversion reaction EQU CO+H.sub.2 0.fwdarw.H.sub.2 +CO.sub.2
with production of hydrogen. Various methods are known for producing the methanol synthesis gas from partial oxidation crude gas. When the catalyst used for the converting reaction is not sulfur resistant, the desulfurization of the gas is performed in many cases also before the conversion and not after the conversion. For the conversion itself it is required that the gas to be converted is loaded with hydrogen before entering the converting reactor and freed from excessive steam after the conversion. So-called moisturizing-demoisturizing systems are known for this purpose. During utilization of sulfur resistant conversion catalysts the loading of the partial oxidation crude gas with hydrogen can be however performed so that it is sprayed directly into the hot gas before the dedusting, and after the conversion the excessive steam is again condensed from the gas. A condensate return into the hot partial oxidation crude gas is however possible only to a limited extent when the gas must be dedusted in a dry process. Depending on the used methods of moisturizing and demoisturizing of the gas, in each case significant heat quantities in low temperature region must be withdrawn with the excess steam condensate. Simultaneously intensive heat exchange for the heating of the gas and the condensation of the excessive steam require considerable apparatus expenses.